The present invention generally relates to a piezoelectric vibrator or resonator and more particularly, to the construction of a piezoelectric vibrator whose vibrating frequency is determined by the dimensions of a piezoelectric plate itself, and to the construction of a piezoelectric vibrator including a piezoelectric transducer and a mechanical vibrating plate, and also to a method of adjusting the vibrating frequencies of such a piezoelectric vibrator.
Conventionally, as a piezoelectric vibrator employing expansion mode vibration directed from a center towards a peripheral portion thereof, there have been mainly proposed crystal vibrators and piezoelectric ceramic vibrators. For setting the vibrating frequency of such a vibrator to a desired value, it has been a common practice to alter the peripheral lengths or the lengths of the sides by trimming off end faces of discs, rectangular or square plates, etc. or to add a mass onto the vibrating surface, but in this case, the vibrator tends to lose its balance, with a consequent adverse effect on the resonance characteristics, while adjustments thereof are difficult, requiring adjusting indices applied thereto.
By way of example, in the case where end faces of a vibrator V in the form of a square plate as shown in FIG. 1 (in which an electrode is omitted for clarity), are to be trimmed for adjustment of the vibrating frequency, four sides of the square plate may be simultaneously trimmed by the same amount, but due to poor processability in that case, sides l1 and l2 are usually trimmed the same amount in the state where l1=l2. In this case, however, since a support point S is undesirably deviated from the center, it has been difficult to eliminate deterioration in the resonance characteristics or to improve accuracy in trimming. Furthermore, difficulties in measurements during the trimming obstruct improvement of the accuracy, and trimming one piece by one piece also results in the requirement of much trimming time or application of adjusting indices.